The Lighthouse is the UK?s first net zero carbon house that also meets Level 6 (the highest level) of the Code for Sustainable Homes, the standard to which all new homes must be constructed by 2016. It is designed to provide a way of living that encourages lifestyles which are inherently ?light? on the world?s resources balancing the practical requirements of homeowners with a response to the expected climate change in the UK.
The project is the result of long-term collaboration between Kingspan, Sheppard Robson, Arup, Davis Langdon and McFarlane Wilder, creating the next generation of housing for sustainable, affordable homes. The prototype was constructed in June this year, at BRE in Watford and will remain on the site for four years where the buildings performance will be monitored.
A catalogue of ?Lighthouse? houses and apartments, following the same design and technological credentials of the prototype, are currently part of large scale mixed-use and residential masterplans, such as Ebbsfleet.
The design and construction of the house proves that a carbon-free house is achievable but it places the responsibility on both the technologies and its user. It is a living experience which relies on the occupant adapting their lifestyle; an action we all need to take if we are to make any real impact on the UK?s environmental future.
The heart of the design concept for the Lighthouse, the prototype of which is 93m2, two and a half storey, two bedroom house, is the ambition to create homes that are attractive; places where the environmental systems and construction methods do not compromise the quality of the occupant?s life but add to it - adaptable, flexible spaces that are designed for modern living, intuitively integrating sustainability. It has been designed in line with Lifetime Homes and Scheme Development Standards.
The structure of the Lighthouse is a simple barnlike form, derived from a 40 degree roof accommodating a PV array. The sweeping roof envelops the central space ? a generous, openplan, top-lit, double height living space, with the sleeping accommodation at ground level. The living space uses a timber portal structure so floors can be slotted between the frames or left open as required.
Stability is achieved through the moment connections at first floor and ceiling level. At ground level a timber frame structural layout carries the vertical loads of the open plan frames above and provides stability to the load bearing shear walls. It is constructed using Kingspan Off-Site?s TEK Building System, a high performance SIPS (structurally insulated panel based system) which, for the Lighthouse, will provide a high level of thermal insulation and performance ? U values of 0.11W/m2K and air-tightness of less than 1.0m3/hr/m2 at 50Pa - reducing the heat loss by potentially two thirds of a standard house. The foundations consist of offsite timber floor cassettes on a ring beam of timber beams supported off the ground level by screw fast pile heads. The piles provide minimal disturbance to the ground and provide suitable supports for domestic scale dwellings. When the building reaches the end of its useful lifespan, the fast foundation support point can be removed.
Inherent to the design of the Lighthouse I the response to the predicted increase in temperature due to climate change, This is achieved through a combination of design techniques and systems.
Solar gain and shading
At Level 6 there is a mandatory heat loss parameter which demands high U-values for the building fabric - 0.8 Watts/m2K for the windows and 0.11Watts/m2K for the walls. As a result the ratio of glazing to wall in the Lighthouse is 18% as opposed to 25-30% in traditional houses. This drove our decision to locate the living space on to the first floor enabling us to maximise daylight and volume, with a top-lit double height living space. Shading to the west elevation is provided by retractable shutters restricting direct sunlight, minimising heat gain in the summer. These can be folded away when not required to shade the space from evening sun. Future temperatures in the UK may reach those similar to southern Europe however our sun angle will remain low; we still need to maximise sun and daylight mid-season and winter. The passive design of the house must balance the technical considerations with the occupants? expectations who are more accustomed to light and airy living.
Selective thermal mass
Phase changing material in the ceilings absorbs the room heat by changing from solid to liquid within microscopic capsules embedded in the board. This process is reversed when the room is cooled with the night air, working with the passive system of the wind catcher.
Wind catcher/light funnel
Located on the roof, above the central void over the staircase, the wind catcher provides passive cooling and ventilation. When open this catches the cold air forcing it down into the heart of the house ? the living space and the ground floor sleeping accommodation, dispersing the hot air, allowing it to escape. The wind catcher also brings daylight deep into the plan of the house and provides the ground floor sleeping accommodation with secure night time ventilation.
Services will be integrated with smart metering and monitoring which records energy consumption and enables occupants to identify if any wastage is occurring, helping to promote more environmentally aware lifestyles.
Renewable energy is provided by a biomass boiler with an automatic feed system for heating, building integrated photovoltaics (BIPV) electricity and a solar-thermal array, which supplies hot water and allows the boiler to be turned off in the summer and turned down in the spring and autumn, significantly reducing fuel consumption.
These renewable energy features have reduced energy fuel costs for space and water heating in the Lighthouse to around ?30 per year and, as all electricity is supplied via solar technologies, electricity running costs are completely eliminated. The overall costs of the fuel has been reduced by about 94% (not including standard charges).
Water efficiency techniques that have been included in the Lighthouse design include low volume, water efficient sanitary ware and appliances, such as spray taps, a dual flush toilet, low flow showers and a small bath. Water from the shower and bath is recycled via a stand-alone grey water system that fits behind the toilet and supplies water for flushing. Rainwater from the roof is collected in a below ground tank in the garden, which is filtered by a rainwater harvesting system and re-used by the washing machine and for watering the garden. Level 6 of the CSH requires that a maximum of 80 litres of water is used per person per day and by using these measures, the Lighthouse is easily able to achieve this.
Lighthouse also includes mechanical ventilation with heat recovery (MVHR), as well as a roof-mounted wind catcher, which provides secure nighttime ventilation for passive cooling, in conjunction with thermal mass boards in the ceilings and external shading. This helps to control the temperature of the interior environment, improving occupier comfort and keeping the house cool in the summer months.
LIGHTHOUSE: FACTS & FIGURES
Energy & carbon dioxide
? Walls, roof, floor U-values = 0.11W/m?K -Tek System, 284mm thick
? Windows = 0.7W/m?K (inc. wooden frame),triple glazed, gas filled
? Air permeability = 1m?/h/m? at 50 Pa
? Thermal bridging 4.5% of surface area
? Mechanical ventilation = 88% heat recovery -Kingspan KAR MVHR
? Specific fan power 0.92W/l/s
? Lighting ? 100% fluorescents
? Drying room with fittings
? Energy labelled A++ white goods
? External lights on PIR (presence detection)
? Home office facilities
? On-site renewable energy: 4.7kW, 46m? photovoltaics
? 10kW automatic wood pellet boiler ? only 2kW needed
? Wood store, filled three times a year
? 4m? solar hot water to reduce wood resource used in summer
Every building material and component used was specified for its ability to optimise the houses? overall sustaubability credentials and minimise embodied energy and maximise recycled content and reuse.
? Timber frame
? Walls and roof ? TEK structurally insulated panels (SIPS)
? Cladding ? sweet chestnut
? Paved surface from recycled or sustainable sources
? Wool carpet
? Improved biodiversity through native planting and creation of surface water environment
Health & Well Being
? Daylight ? 1.5 -2% daylight factors
? Design of private spaces
? Built to Lifetime Homes standards
? Cycle store
? Potable water reduction: Low water shower 8 litres/min and taps
? Dual flush WC, 4/2 litres, 160 litre bath
? Water labelled A++ washing white goods
? Greywater recycling for WC flushing
? Rainwater harvesting for washing machine and irrigation.
? Surface water run off/
? Bio-filtration through surface water management ? swales
CARBON FOOTPRINT: ENERGY USE
The energy use has been calculated using an adapted SAP method. SAP (Standard Assessment Procedure) is the calculation method used for the energy assessment for checking Building Regulations compliance for dwellings.
The heating energy is calculated using a degree day method.
SAP has been adapted as follows:
? 100% low energy lighting rather than 30%
? 0% secondary heating rather than 10% electrical
? 88% heat recovery efficiency rather than 66%
? specific fan power (SFP) of 0.92 W/l/s rather than 2 W/ l/s
? 2940 kWh/yr solar thermal (calculated by manufacturer) rather than 1475 kWh/yr
? water heating based on reduced shower water flow rate
The energy cost of running the Lighthouse would be about ?31 per year for the wood pellets, assuming wood pellets cost 1.8 p/ kWh. The electricity is free, from the sun. Most of the domestic hot water energy is provided by the solar thermal panels. There is a small amount of carbon dioxide emissions associated with the growing, processing and delivery of the wood pellets for the remainder of the hot water and for the space heating. This is offset by extra renewable electricity that is generated from the sun by the photovoltaic panels and exported to the grid. In this way, the house is net zero carbon on an annual basis.
A house of the same size and shape but built to 2006 Building Regulations standards would cost about ?500 a year in energy bills.
THE LIGHTHOUSE CATALAGUE: MASTERPLANNING
The catalogue of houses demonstrates how the Lighthouse can accommodate variations in orientation and mix.
Different densities and diversities with in a masterplan introduce different renewable energy sources and systems. However, achieving the highest code, level 6, relies on PV?s to generate electricity demand. This results in a rigorous orientation with large roof areas facing the south. For larger development, biomass, combined heat and power or large scale wind ease the demand on PV?s allowing greater flexibility in the masterplan.